Mr Hastie was called to give evidence in defamation proceedings launched by the Victoria Cross recipient over allegations he committed war crimes in Afghanistan, bullied colleagues, and assaulted his mistress.
The 43-year-old denies all the allegations reported by The Age, The Sydney Morning Herald and The Canberra Times, who are defending them as true.
Mr Hastie - who served in the Special Air Service Regiment between 2010 and 2015 and is now assistant minister for defence - on Thursday told the court there was a "widespread, prevailing" view that Mr Roberts-Smith had bullied at least one of his comrades, codenamed Person One.
Person One has previously told the court he had formally reported Mr Roberts-Smith for a years-long campaign of "ruthless and unwavering aggression" that included threats, spitting on the ground in front of him, slamming doors in his face, and hitting him across the back of the head while he was driving.
Mr Hastie recounted sitting down for breakfast in 2012 with a group of his colleagues when Mr Roberts-Smith appeared on TV, talking about the mental health charities he supported.
"Person 68 stopped… and said loudly, 'RS gave Person One depression, now he's gonna help him fight it'."
"Everyone laughed ... but not at the expense of Person One."
Mr Hastie also recounted some of his own interactions with Mr Roberts-Smith, including during a mission when he is accused of forcing a subordinate to kill a detained Afghan.
"We heard on the radio 'shots fired'. I didn't hear a shot," Mr Hastie said.
Mr Roberts-Smith soon walked past him.
"He looked me in the eye and said 'just a couple more dead c***s'."
Mr Hastie also told the court Mr Roberts-Smith had once said to him officers like Mr Hastie should be kept away from the action because they just get in the way.
Earlier on Thursday, Mr Roberts-Smith's barrister grilled his former mistress over her domestic violence allegations, saying she made up a pregnancy to stop the war hero dumping her.
When he eventually left her, she also invented the assault claims, he said.
The woman - codenamed Person 17 - had previously told the court the pair's intense relationship in 2017 and 2018 had culminated in Mr Roberts-Smith deleting messages off her phone, making veiled threats, punching her, and taking naked photos of her while she was asleep.
She has told the Federal Court she miscarried in the days before she was due to travel to Brisbane to have an abortion as agreed, but hadn't told Mr Roberts-Smith as she wanted to break the news in person.
Bruce McClintock put to the woman that she had waged a calculated campaign of deceit, something the woman denies.
She only owned up to forgoing the termination when she was "caught out" and confronted by videos taken by a private investigator hired by Mr Roberts-Smith.
She then told him she had miscarried.
"Were you ever actually pregnant?" Mr McClintock asked.
"Yes," the woman replied.
She previously told the court she had done a pregnancy test in front of Mr Roberts-Smith, something Mr McClintock said never happened.
Mr McClintock also suggested the black eye she says was a result Mr Roberts-Smith punching her in the face was actually caused when she hit her head during a drunken fall.
He quizzed her over her evidence that she had twice unsuccessfully tried to report the alleged assault to police, accusing her of making up the visits.
The court was later shown records of an attendance taken by the police stations.
However, Mr McClintock noted neither mentioned alleged assault, which the woman said she was hesitant to do until speaking with someone senior as she was scared of Mr Roberts-Smith's connections.
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